They are worth it if you can find a great one, what your best doing, is.....
Waiting for a huge site thats going to have a lot of hype like before bebo and faceparty got so big, or like digg
If you think its going to be popular dive in
Sit for like 10 minutes in notepad.exe and type real fast for example
amazon.com sit and try and type that shit real fast in notepad around 10 times then buy the available ones.
amaozna
amazon
amaozn
amaozn
amaonz
amaon
amzon

then .com them all

Redirect it to an affiliate program if it has it and it will most likely go unnoticed.
But trust me its not worth going for a site thats stupid.
The only ones that are worth it are high traffic although some people like to buy forum typins like blackhatworldcom.com as some browsers would forward blackhatworldcom (if you type that in bar and hit enter) to blackhatworldcom.com first